2018-08-22 UTC
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sknebel for reference, here's what the normal feeds do: https://github.com/WordPress/WordPress/blob/master/wp-includes/default-filters.php#L203 via https://github.com/WordPress/WordPress/blob/7dfcb33d4dddf8b6098e8846c9ed99017bfb5877/wp-includes/feed.php#L153